To provide a process whereby an ultrafine fiber of a fluorinated ion exchange resin can be produced easily at low cost, and a method whereby a catalyst layer having a high gas diffusion property can be produced easily at low cost.A process for producing a fiber by spinning a spinning solution containing a fluorinated ion exchange resin and a solvent by a dry spinning method, or producing an electrically conductive composite fiber by spinning n types (where n is an integer of at least 2) of spinning solutions, of which at least one type contains a fluorinated ion exchange resin and a solvent, and at least one type contains an electrically conductive material and a solvent, simultaneously by a dry spinning method, wherein the spinning solution which is being spun by the dry spinning method, is stretched by a gas stream; and a method for producing a catalyst layer, which comprises accumulating the fiber produced by such a process to form a non-woven fabric thereby to obtain a catalyst layer having the non-woven fabric.